Monodisperse aerosol generator for use with infrared spectrometry

Abstract

A monodisperse aerosol generator forms a stable jet of liquid at a velocity allowing columnar breakup into droplets of uniform size and spacing. To prevent degradation of the monodisperse aerosol, it is disposed by entrainment in a high velocity gaseous stream. To provide an interface for direct injection onto a particle collection device or into an infrared or Raman spectrometer or to interface a liquid chromatograph with a particle collection device or an infrared or Raman spectrometer, the generator is followed by a desolvation chamber operation at about atmospheric pressure and a multistage pressure reducer which evacuates solvent vapor and gaseous medium to form a high momentum, solvent-depleted solute aerosol beam which is input into the infrared or Raman spectrometer.

What is claimed is: 
     
       1. A method of introducing solute into an infrared or Roman spectrometer, which comprises the steps of: (a) providing a solution including a relatively volatile solvent and a relatively involatile solute;   (b) generating an aerosol from the solution by delivering the solution through a conduit at a velocity such that formation of droplets with a narrow size distribution occurs;   (c) providing a dispersing gas;   (d) dispersing the formed droplets with the gas;   (e) entraining the aerosol in gas and desolvating the aerosol at substantially atmospheric pressure;   (f) expanding the components of step (e) into low pressure environment while removing gas therefrom to form a high momentum aerosol beam of solute particles with a narrow particle size distribution; and   (g) directing said beam into an infrared or Roman spectrometer.   
     
     
       2. A method as defined in claim 1, wherein said beam is directed onto a collection surface in the infrared or Raman spectrometer. 
     
     
       3. A method as defined in claim 1, wherein an infrared beam directly interacts with the beam of solute particles. 
     
     
       4. A method as defined in claim 3, wherein the beam of solute particles is subsequently directed onto a collection surface. 
     
     
       5. A method as defined in claim 1, wherein the beam of solute particles is subsequently directed from the infrared or Raman spectrometer into a mass spectrometer. 
     
     
       6. A method as defined in claim 1, wherein the solution is provided from the effluent of a liquid chromatograph. 
     
     
       7. A system for introducing solvent depleted solute into an infrared or Raman spectrometer which comprises: (a) means for providing a solution including a relatively volatile solvent and a relatively involatile solute;   (b) means for generating a monodisperse aerosol from the solution by supplying the solution to a nozzle at a rate sufficient to produce a stable jet of liquid having a velocity such that monodisperse droplet breakup of the jet occurs;   (c) dispersing means for entraining the droplets after the point of droplet formation in a high velocity flow of gas so as to retain the monodisperse nature thereof;   (d) a desolvating chamber for producing the solvent depleted solute;   (e) pressure reduction means for expanding said gas with entrained droplets into a low pressure environment while removing gas therefrom to form a high monentum monodisperse aerosol beam of solute particles; and   (f) means for directing said beam into an infrared or Raman spectrometer.   
     
     
       8. The system of claim 7 wherein said pressure reduction means includes a first vacuum chamber having a pressure in the range of 2-20 torr. 
     
     
       9. The system of the claim 7 where said pressure reduction means further comprises two vacuum chambers, the second having a pressure in the range of 0.01 to 10 torr.   
     
     
       10. The system of claim 7, wherein said desolvating chamber is maintained at about atmospheric pressure. 
     
     
       11. The system of claim 7, further comprising a vacuum chamber for continuously evacuating gaseous medium and a vacuum pump which maintains said vacuum chamber at a pressure in the range of 2-20 torr. 
     
     
       12. The system of claim 11, further comprising a second vacuum chamber and a second vacuum pump which maintains said second vacuum chamber at a pressure in the range of 0.01 to 10 torr. 
     
     
       13. The system of claim 7, further comprising a collection surface onto which the beam of particles is directed. 
     
     
       14. The system of claim 7, further comprising means for directing the particle beam from the infrared or Raman spectrometer into a mass spectrometer.